From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Klaudia Kloc <klaudia@vidocsecurity.com>,
	=?UTF-8?q?Dawid=20Moczad=C5=82o?= <dawid@vidocsecurity.com>,
	Jenny Guanni Qu <qguanni@gmail.com>,
	Florian Westphal <fw@strlen.de>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.1 418/481] netfilter: xt_time: use unsigned int for monthday bit shift
Date: Mon, 23 Mar 2026 14:46:40 +0100
Message-ID: <20260323134535.379148115@linuxfoundation.org>
In-Reply-To: <20260323134525.256603107@linuxfoundation.org>
References: <20260323134525.256603107@linuxfoundation.org>
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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jenny Guanni Qu <qguanni@gmail.com>

[ Upstream commit 00050ec08cecfda447e1209b388086d76addda3a ]

The monthday field can be up to 31, and shifting a signed integer 1
by 31 positions (1 << 31) is undefined behavior in C, as the result
overflows a 32-bit signed int. Use 1U to ensure well-defined behavior
for all valid monthday values.

Change the weekday shift to 1U as well for consistency.

Fixes: ee4411a1b1e0 ("[NETFILTER]: x_tables: add xt_time match")
Reported-by: Klaudia Kloc <klaudia@vidocsecurity.com>
Reported-by: Dawid Moczadło <dawid@vidocsecurity.com>
Tested-by: Jenny Guanni Qu <qguanni@gmail.com>
Signed-off-by: Jenny Guanni Qu <qguanni@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/netfilter/xt_time.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/xt_time.c b/net/netfilter/xt_time.c
index 6aa12d0f54e23..61de85e02a40f 100644
--- a/net/netfilter/xt_time.c
+++ b/net/netfilter/xt_time.c
@@ -227,13 +227,13 @@ time_mt(const struct sk_buff *skb, struct xt_action_param *par)
 
 	localtime_2(&current_time, stamp);
 
-	if (!(info->weekdays_match & (1 << current_time.weekday)))
+	if (!(info->weekdays_match & (1U << current_time.weekday)))
 		return false;
 
 	/* Do not spend time computing monthday if all days match anyway */
 	if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) {
 		localtime_3(&current_time, stamp);
-		if (!(info->monthdays_match & (1 << current_time.monthday)))
+		if (!(info->monthdays_match & (1U << current_time.monthday)))
 			return false;
 	}
 
-- 
2.51.0